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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2011 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except<a name="line.4"></a>
<span class="sourceLineNo">005</span> * in compliance with the License. You may obtain a copy of the License at<a name="line.5"></a>
<span class="sourceLineNo">006</span> *<a name="line.6"></a>
<span class="sourceLineNo">007</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.7"></a>
<span class="sourceLineNo">008</span> *<a name="line.8"></a>
<span class="sourceLineNo">009</span> * Unless required by applicable law or agreed to in writing, software distributed under the License<a name="line.9"></a>
<span class="sourceLineNo">010</span> * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express<a name="line.10"></a>
<span class="sourceLineNo">011</span> * or implied. See the License for the specific language governing permissions and limitations under<a name="line.11"></a>
<span class="sourceLineNo">012</span> * the License.<a name="line.12"></a>
<span class="sourceLineNo">013</span> */<a name="line.13"></a>
<span class="sourceLineNo">014</span><a name="line.14"></a>
<span class="sourceLineNo">015</span>package com.google.common.hash;<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>import com.google.common.annotations.Beta;<a name="line.17"></a>
<span class="sourceLineNo">018</span>import com.google.common.base.Preconditions;<a name="line.18"></a>
<span class="sourceLineNo">019</span>import com.google.common.primitives.Ints;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.security.MessageDigest;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>import javax.annotation.Nullable;<a name="line.23"></a>
<span class="sourceLineNo">024</span><a name="line.24"></a>
<span class="sourceLineNo">025</span>/**<a name="line.25"></a>
<span class="sourceLineNo">026</span> * An immutable hash code of arbitrary bit length.<a name="line.26"></a>
<span class="sourceLineNo">027</span> *<a name="line.27"></a>
<span class="sourceLineNo">028</span> * @author Dimitris Andreou<a name="line.28"></a>
<span class="sourceLineNo">029</span> * @since 11.0<a name="line.29"></a>
<span class="sourceLineNo">030</span> */<a name="line.30"></a>
<span class="sourceLineNo">031</span>@Beta<a name="line.31"></a>
<span class="sourceLineNo">032</span>public abstract class HashCode {<a name="line.32"></a>
<span class="sourceLineNo">033</span>  HashCode() {}<a name="line.33"></a>
<span class="sourceLineNo">034</span><a name="line.34"></a>
<span class="sourceLineNo">035</span>  /**<a name="line.35"></a>
<span class="sourceLineNo">036</span>   * Returns the first four bytes of {@linkplain #asBytes() this hashcode's bytes}, converted to<a name="line.36"></a>
<span class="sourceLineNo">037</span>   * an {@code int} value in little-endian order.<a name="line.37"></a>
<span class="sourceLineNo">038</span>   */<a name="line.38"></a>
<span class="sourceLineNo">039</span>  public abstract int asInt();<a name="line.39"></a>
<span class="sourceLineNo">040</span><a name="line.40"></a>
<span class="sourceLineNo">041</span>  /**<a name="line.41"></a>
<span class="sourceLineNo">042</span>   * Returns the first eight bytes of {@linkplain #asBytes() this hashcode's bytes}, converted to<a name="line.42"></a>
<span class="sourceLineNo">043</span>   * a {@code long} value in little-endian order.<a name="line.43"></a>
<span class="sourceLineNo">044</span>   *<a name="line.44"></a>
<span class="sourceLineNo">045</span>   * @throws IllegalStateException if {@code bits() &lt; 64}<a name="line.45"></a>
<span class="sourceLineNo">046</span>   */<a name="line.46"></a>
<span class="sourceLineNo">047</span>  public abstract long asLong();<a name="line.47"></a>
<span class="sourceLineNo">048</span><a name="line.48"></a>
<span class="sourceLineNo">049</span>  /**<a name="line.49"></a>
<span class="sourceLineNo">050</span>   * If this hashcode has enough bits, returns {@code asLong()}, otherwise returns a {@code long}<a name="line.50"></a>
<span class="sourceLineNo">051</span>   * value with {@code asInt()} as the least-significant four bytes and {@code 0x00} as<a name="line.51"></a>
<span class="sourceLineNo">052</span>   * each of the most-significant four bytes.<a name="line.52"></a>
<span class="sourceLineNo">053</span>   *<a name="line.53"></a>
<span class="sourceLineNo">054</span>   * @since 14.0 (since 11.0 as {@code Hashing.padToLong(HashCode)})<a name="line.54"></a>
<span class="sourceLineNo">055</span>   */<a name="line.55"></a>
<span class="sourceLineNo">056</span>  public abstract long padToLong();<a name="line.56"></a>
<span class="sourceLineNo">057</span><a name="line.57"></a>
<span class="sourceLineNo">058</span>  /**<a name="line.58"></a>
<span class="sourceLineNo">059</span>   * Returns the value of this hash code as a byte array. The caller may modify the byte array;<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * changes to it will &lt;i&gt;not&lt;/i&gt; be reflected in this {@code HashCode} object or any other arrays<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * returned by this method.<a name="line.61"></a>
<span class="sourceLineNo">062</span>   */<a name="line.62"></a>
<span class="sourceLineNo">063</span>  // TODO(user): consider ByteString here, when that is available<a name="line.63"></a>
<span class="sourceLineNo">064</span>  public abstract byte[] asBytes();<a name="line.64"></a>
<span class="sourceLineNo">065</span><a name="line.65"></a>
<span class="sourceLineNo">066</span>  /**<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * Copies bytes from this hash code into {@code dest}.<a name="line.67"></a>
<span class="sourceLineNo">068</span>   *<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * @param dest the byte array into which the hash code will be written<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * @param offset the start offset in the data<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * @param maxLength the maximum number of bytes to write<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * @return the number of bytes written to {@code dest}<a name="line.72"></a>
<span class="sourceLineNo">073</span>   * @throws IndexOutOfBoundsException if there is not enough room in {@code dest}<a name="line.73"></a>
<span class="sourceLineNo">074</span>   */<a name="line.74"></a>
<span class="sourceLineNo">075</span>  public int writeBytesTo(byte[] dest, int offset, int maxLength) {<a name="line.75"></a>
<span class="sourceLineNo">076</span>    byte[] hash = asBytes();<a name="line.76"></a>
<span class="sourceLineNo">077</span>    maxLength = Ints.min(maxLength, hash.length);<a name="line.77"></a>
<span class="sourceLineNo">078</span>    Preconditions.checkPositionIndexes(offset, offset + maxLength, dest.length);<a name="line.78"></a>
<span class="sourceLineNo">079</span>    System.arraycopy(hash, 0, dest, offset, maxLength);<a name="line.79"></a>
<span class="sourceLineNo">080</span>    return maxLength;<a name="line.80"></a>
<span class="sourceLineNo">081</span>  }<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span>  /**<a name="line.83"></a>
<span class="sourceLineNo">084</span>   * Returns the number of bits in this hash code; a positive multiple of 32.<a name="line.84"></a>
<span class="sourceLineNo">085</span>   */<a name="line.85"></a>
<span class="sourceLineNo">086</span>  public abstract int bits();<a name="line.86"></a>
<span class="sourceLineNo">087</span><a name="line.87"></a>
<span class="sourceLineNo">088</span>  @Override public boolean equals(@Nullable Object object) {<a name="line.88"></a>
<span class="sourceLineNo">089</span>    if (object instanceof HashCode) {<a name="line.89"></a>
<span class="sourceLineNo">090</span>      HashCode that = (HashCode) object;<a name="line.90"></a>
<span class="sourceLineNo">091</span>      // Undocumented: this is a non-short-circuiting equals(), in case this is a cryptographic<a name="line.91"></a>
<span class="sourceLineNo">092</span>      // hash code, in which case we don't want to leak timing information<a name="line.92"></a>
<span class="sourceLineNo">093</span>      return MessageDigest.isEqual(this.asBytes(), that.asBytes());<a name="line.93"></a>
<span class="sourceLineNo">094</span>    }<a name="line.94"></a>
<span class="sourceLineNo">095</span>    return false;<a name="line.95"></a>
<span class="sourceLineNo">096</span>  }<a name="line.96"></a>
<span class="sourceLineNo">097</span><a name="line.97"></a>
<span class="sourceLineNo">098</span>  /**<a name="line.98"></a>
<span class="sourceLineNo">099</span>   * Returns a "Java hash code" for this {@code HashCode} instance; this is well-defined<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * (so, for example, you can safely put {@code HashCode} instances into a {@code<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * HashSet}) but is otherwise probably not what you want to use.<a name="line.101"></a>
<span class="sourceLineNo">102</span>   */<a name="line.102"></a>
<span class="sourceLineNo">103</span>  @Override public int hashCode() {<a name="line.103"></a>
<span class="sourceLineNo">104</span>    /*<a name="line.104"></a>
<span class="sourceLineNo">105</span>     * As long as the hash function that produced this isn't of horrible quality, this<a name="line.105"></a>
<span class="sourceLineNo">106</span>     * won't be of horrible quality either.<a name="line.106"></a>
<span class="sourceLineNo">107</span>     */<a name="line.107"></a>
<span class="sourceLineNo">108</span>    return asInt();<a name="line.108"></a>
<span class="sourceLineNo">109</span>  }<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span>  /**<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * Returns a string containing each byte of {@link #asBytes}, in order, as a two-digit unsigned<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * hexadecimal number in lower case.<a name="line.113"></a>
<span class="sourceLineNo">114</span>   *<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * &lt;p&gt;Note that if the output is considered to be a single hexadecimal number, this hash code's<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * bytes are the &lt;i&gt;big-endian&lt;/i&gt; representation of that number. This may be surprising since<a name="line.116"></a>
<span class="sourceLineNo">117</span>   * everything else in the hashing API uniformly treats multibyte values as little-endian. But<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * this format conveniently matches that of utilities such as the UNIX {@code md5sum} command.<a name="line.118"></a>
<span class="sourceLineNo">119</span>   */<a name="line.119"></a>
<span class="sourceLineNo">120</span>  @Override public String toString() {<a name="line.120"></a>
<span class="sourceLineNo">121</span>    byte[] bytes = asBytes();<a name="line.121"></a>
<span class="sourceLineNo">122</span>    // TODO(user): Use c.g.common.base.ByteArrays once it is open sourced.<a name="line.122"></a>
<span class="sourceLineNo">123</span>    StringBuilder sb = new StringBuilder(2 * bytes.length);<a name="line.123"></a>
<span class="sourceLineNo">124</span>    for (byte b : bytes) {<a name="line.124"></a>
<span class="sourceLineNo">125</span>      sb.append(hexDigits[(b &gt;&gt; 4) &amp; 0xf]).append(hexDigits[b &amp; 0xf]);<a name="line.125"></a>
<span class="sourceLineNo">126</span>    }<a name="line.126"></a>
<span class="sourceLineNo">127</span>    return sb.toString();<a name="line.127"></a>
<span class="sourceLineNo">128</span>  }<a name="line.128"></a>
<span class="sourceLineNo">129</span><a name="line.129"></a>
<span class="sourceLineNo">130</span>  private static final char[] hexDigits = "0123456789abcdef".toCharArray();<a name="line.130"></a>
<span class="sourceLineNo">131</span>}<a name="line.131"></a>




























































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